Pedicle screw assembly

ABSTRACT

A medical device and methods of use thereof are provided for supporting a structure (e.g., bone). A screw assembly is provided that is comprised of a base, an arm, and an interconnection means for coupling the base to the arm. The interconnection means allows the arm to be positionable in a first position that is parallel to a long axis of the base and positionable in a second position that is perpendicular to the long axis of the base. The base is configured for attachment to a structure and the arm configured for attachment to a support structure. A support structure is provided that includes one or more receivers having locking means, which can be configured as an open-ended saddle for attachment to a medical device (e.g., a screw assembly). The support structure is configured to receive one or more medical devices and lock the medical devices to the support structure after installation in a patient.

TECHNICAL FIELD

This invention relates to medical devices.

BACKGROUND

The use of bone stabilization/fixation devices to align or positionbones is well established. Furthermore, the use of spinal bonestabilization/fixation devices to align or position specific vertebraeor a region of the spine is well established. Typically such devices forthe spine utilize a spinal fixation element, comprised of a relativelyrigid member such as a plate, board or rod that is used as a couplerbetween adjacent vertebrae. Such a spinal fixation element can effect arigid positioning of adjacent vertebrae when attached to the pedicleportion of the vertebrae using pedicle bone anchorage screws. Once thecoupled vertebrae are spatially fixed in position, procedures can beperformed, healing can proceed or spinal fusion may take place.

Spinal fixation elements may be introduced to stabilize the variousvertebrae of the spine. Some devices for this purpose are designed to beattached directly to the spine, but the generally invasive nature ofstandard paraspinal approach used to implant these devices posesdrawbacks. For example, the use of conventional pedicle screws and hooksis a relatively invasive protocol resulting in muscle disruption andblood loss.

SUMMARY

In general, in one aspect, the invention provides a medical device forsupporting a structure comprising a screw assembly. The screw assemblyincludes a base, an arm, and an interconnection means for coupling thebase to the arm. The interconnection means allows the arm to bepositionable in a first position that is parallel to a long axis of thebase and positionable in a second position that is perpendicular to thelong axis of the base. The base is configured for attachment to astructure in a patient and the arm configured for attachment to asupport structure. In one implementation, the structure attached to isbone.

The device can include a support structure and the screw assembly can beattached to the support structure by the arm. Alternatively, two screwassemblies can be attached to the support structure.

The screw assembly can be comprised of a material selected from thegroup consisting of titanium, stainless steel, carbon fiber, shapememory metal, a biocompatible material and a reabsorbable material and acomposite or combination thereof. Alternatively, the screw assembly canbe comprised of a continuous piece of shape memory metal. In oneimplementation the interconnection means is comprised of shape memorymetal. In another implementation, the screw assembly, including theinterconnection means is comprised of a piece of metal suited forbending.

The screw assembly can be of varying lengths, including an overalllength in the range substantially between 0.1 and 100 centimeters. Inone implementation, the overall length is in the range substantiallybetween 50 and 600 millimeters. In another implementation, the screwassembly has an overall length sized for subcutaneous support of thespine. In yet another implementation, the screw assembly has an overalllength sized for subcutaneous support of the posterior of a spine.

The arm of the screw assembly can be comprised of a body, a base yokeand a connector end. The body of the arm can be any of a number ofshapes including rod shaped.

The base of the screw assembly can be comprised of a base head and ananchor. The anchor can be selected from the group consisting of a screw,staple, hook or nail. In one implementation the anchor is a screwconfigured for bone anchoring. In another implementation, the anchor isa screw configured for insertion into the pedicle of a vertebrae.

The interconnection means of the screw assembly can be of any of anumber of configurations. In one implementation, the interconnectionmeans includes a press-fit cross pin. In another implementation theinterconnection means is comprised of an open saddle head andcoupling-cross piece. The interconnection means can also include asetscrew, wherein the setscrew holds the arm and the base together as asingle unit. Additionally, the setscrew can be tightened within theinterconnection means to effect locking of the arm in a position that issubstantially perpendicular to the long axis of the base. In anotherimplementation, the locking means can also include a cam that canfunction analogously to the setscrew.

In one implementation, the device can be comprised of one screw assemblyand a support structure, wherein the support structure includes a topsurface, a bottom surface, an aperture and two receivers. In thisimplementation, the aperture can pass from the top surface through tothe bottom surface of the support structure, wherein an anchor isdisposed within the central aperture in an orientation substantiallyperpendicular to the top surface of the support structure.

The support structure of the device can be comprised of a top surface, abottom surface and two receivers. Each receiver can include anopen-ended saddle type receiver configured for attachment of one or moremedical devices. Additionally, each receiver can include a lockingmeans. The locking means can be a setscrew or cam. The locking means canbe oriented within the plane of the top surface such that access to thelocking means is from the top surface. The support structure can beconfigured to receive the medical devices and lock the medical devicesto the support structure after the support structure has been installed.

The support structure can be comprised of a material selected from thegroup consisting of titanium, stainless steel, carbon fiber, abiocompatible material, a reabsorbable material and a composite orcombination thereof. Additionally, the support structure can include acentral aperture passing from the top surface through to the bottomsurface of the support structure. An anchor can be disposed within thecentral aperture in an orientation substantially perpendicular to thetop surface of the support structure. Alternatively, the supportstructure can include a central hinged claw having a threadedhinge-engagement member and nut disposed on the top surface. In use,tightening the nut onto the threaded hinge-engagement member causes apivoting about the hinge to effect closing of the claw.

The device can be comprised of two screw assemblies and a supportstructure, wherein each screw assembly includes a base, an arm, and aninterconnection means for coupling the base to the arm. Theinterconnection means allows the arm to be positionable in a firstposition that is parallel to a long axis of the base and positionable ina second position that is perpendicular to the long axis of the base. Inthis implementation, the base can be configured for attachment to astructure in a patient and the arm configured for attachment to thesupport structure. In one implementation, the structure attached to isbone. Additionally, the support structure can include a top surface, abottom surface and two receivers, wherein each receiver includes anopen-ended saddle type receiver configured for attachment to a medicaldevice (e.g., screw assembly). The support structure can also include alocking means, to lock medical devices to the support structure afterthe support structure has been installed in a patient. The locking meanscan be setscrews or cams. Furthermore, the support structure in thisimplementation can include an anchor configured for attachment to astructure in a patient. In one implementation, the structure attached toin a patient is bone. Additionally, the anchor can be selected from thegroup consisting of a screw, staple, hook or a nail.

A method of use of the invention for supporting the spine, can includethe steps of: 1) delivering to bone, two screw assemblies having arms,bases and interconnection means; 2) delivering to the vicinity of bone,a support structure having two receivers having locking means for thearms of the screw assemblies; 3) deploying the arms of the screwassemblies; and 4) engaging the locking means of the receivers to securethe arms of the screw assemblies to the support structure.

Another method of use of the invention for supporting the spine, caninclude the steps of: 1) delivering to bone, two screw assemblies havingarms, bases and interconnection means; 2) delivering to bone, a supportstructure having a central aperture with a locking means and an anchor,and two receivers having locking means for the arms of the screwassemblies; 3) deploying the arms of the screw assemblies; and 4)engaging the locking means of the receivers to secure the arms of thescrew assemblies to the support structure.

Yet another method of use of the invention for supporting the spine, caninclude the steps of: 1) delivering to bone, a screw assembly having anarm, base and interconnection means; 2) delivering to bone, a supportstructure having a central aperture with a locking means and an anchor,and a receiver having locking means for the arm of a screw assembly; 3)deploying the arm of the screw assembly; and 4) engaging the lockingmeans of the receiver to secure the arm of the screw assembly to thesupport structure.

In a further implementation, the medical device support structure caninclude an anchor, a receiver, and a locking means; wherein the anchoris configured for attachment to a structure in a patient. The receivercan include an open end for attachment to a medical device (e.g., ascrew assembly). The locking means can be configured to lock the medicaldevice to the support structure, after the support structure has beendeployed in a patient. In one implementation, the structure is bone. Thelocking means can be a setscrew or a cam. The anchor can be selectedfrom the group consisting of a screw, staple, hook or nail. In anotherimplementation, the receiver can include a plurality of receivers oropenings for receiving medical devices.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the invention will be apparent from thedescription and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1A is a drawing of a screw assembly showing the screw assembly, armand base in a first position.

FIG. 1B is a drawing showing the screw assembly in a second position.

FIG. 1C is a drawing showing the screw assembly including a press-fitcross pin-type interconnection means.

FIG. 1D is a drawing showing an open saddle-type base head.

FIG. 1E is a drawing showing an integrally disposed crosspiece.

FIG. 1F is a drawing showing a press-fit cross pin.

FIG. 2A is a drawing showing a support structure.

FIG. 2B is a drawing showing the support structure including a centralaperture and an anchor.

FIG. 2C is a drawing showing the support structure including a hingedclaw.

FIG. 3A is a drawing showing two screw assemblies connected by a supportstructure.

FIG. 3B is a drawing showing two screw assemblies connected by a supportstructure implanted into the pedicles of the vertebrae of the spine.

FIG. 4 is a drawing showing one screw assembly connected to a supportstructure having a central aperture and an anchor.

FIG. 5 is a drawing showing one screw assembly connected to a basehaving an open saddle-type head.

FIG. 6 is a drawing showing cannulas and a support structure tool usedfor implanting the screw assembly and support structure.

FIG. 7 is a drawing of a screw assembly tool used for manipulating thescrew assembly during implantation of the screw assembly in the spine.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

As shown in FIGS. 1A and 1B, a screw assembly 1 is provided comprised ofan arm 2 and a base 3 in a single unit. The screw assembly 1 is elongateand the arm 2 and base 3 of the screw assembly 1, are coupled by aninterconnections means 4. Additionally, as shown in FIGS. 1A and 1B, theinterconnection means 4 facilitates movement between the arm 2 and thebase 3, such that the arm 2 is positionable in a first position that isparallel to a long axis of the base 3 (shown in FIG. 1A) andpositionable in a second position that is perpendicular to the long axisof the base 3 (shown in FIG. 1B). The base 3 of the screw assembly 1 isconfigured for attachment to a structure (e.g., a bone) and the arm 2 isconfigured for attachment to a support structure 10 (described in detailbelow). In application, one or more screw assemblies 1 are attached to asupport structure 10. Preferably, two screw assemblies 1 are attached toa single support structure 10.

In an alternative screw assembly 1 implementation, the arm 2 and base 3of the screw assembly 1 are configured as one continuous piece of shapememory metal. In this implementation, the interconnection means 4 iscomprised of a shape memory metal that can facilitate movement of thearm 2 relative to the base 3 depending on preset conditions affectingthe shape memory metal shape (not shown). In another alternative screwassembly 1 implementation, the arm 2 and base 3 of the screw assembly 1are configured as one continuous piece wherein the interconnection means4 between the arm 2 and base 3 is comprised of a material suited forbending (not shown).

As shown in FIG. 1A, in certain embodiments, the arm 2 feature of thescrew assembly 1 is comprised of a body 17, base yoke 18 and a connectorend 12. The body 17 of the arm 2 can vary in shape and length with theapplication. In one implementation, the body 17 of the arm 2 isrod-shaped (see FIGS. 1A and 1B). Alternatively, the arm 2 body 17 isshaped to substantially fit within a screw assembly tool 19 formanipulating the screw assembly 1. An example of such a screw assemblytool 19 is illustrated in FIG. 7.

The screw assembly 1 can be made of numerous materials that are durableand that can be implanted in a body, including titanium, stainlesssteel, carbon fiber, biocompatible material, etc. In one implementation,the screw assembly 1 is made of titanium. Additionally, the screwassembly 1 can be made of a reabsorbable material or shape memory metal.Alternatively, the screw assembly 1 can be a composite or combination ofany of the foregoing. The dimensions of the screw assembly 1 vary withthe application. In general, the length of the screw assembly 1 is from0.1 to 100 centimeters. In one implementation, the length issubstantially between 50 and 600 millimeters. In another implementation,the screw assembly 1 is sized for applications involving support of theposterior of the spine 28 (see FIG. 3B).

As shown in FIG. 1A, the base 2 of the screw assembly 1 is comprised ofa base head 20 and an anchor 14. The anchor 14 can be a screw, staple,hook or nail and can be of a type typically used for bone anchoring. Inone implementation the anchor 14 is a screw of a type for insertion intoa pedicle 26 of a vertebrae 27 (see FIGS. 1A and 3B).

As shown in FIG. 1C, the interconnection means 4 of the screw assembly 1can be a press-fit cross pin type. In this implementation, the base head20 is a press-fit cross pin-type head 5, and the yoke 18 of the arm 2includes a pin hole 25, wherein the arm 2 and base 3 are pre-assembledincluding a press-fit cross pin (not shown) and a setscrew 9 (notshown). In an alternative implementation, as shown in FIGS. 1D-F, theinterconnection means 4 is configured as an open saddle head withcoupling-cross piece. In this implementation, the base head 20 isconfigured as an open saddle-type head 6 (shown in FIG. 1D), which ispre-assembled with a complementary arm 2 feature. As shown in FIG. 1E,the arm 2 feature that is complementary to the open saddle-type head 6can be a one-piece integrally disposed crosspiece 7. Alternatively, asshown in FIG. 1F, the complementary arm 2 feature can be a press-fitcross pin 8.

As shown in FIGS. 1A and 1B, the arm 2 and base 3 can be held togetheras a single unit by the set screw 9 where the interconnection means 4 isof the form of a press-fit cross pin-type or an open saddle-type head 6with a coupling cross piece. In certain implementations, the opensaddle-type head 6 is threaded to receive the setscrew 9.

Additionally, as shown in FIGS. 1A and 1B, the setscrew 9 can effectlocking of the arm 2 into a fixed position. Prior to moving the arm 2into the deployed position, the setscrew 9 is loosely set in place. Upondeployment, the arm 2 can be locked in a position that is substantiallyperpendicular to the long axis of the base 3 by tightening the setscrew9 into the threaded open saddle head 6 of the base 3 (see FIG. 1B).

In one implementation, locking of the arm 2 position and holding the arm2 and base 3 together as a single unit can be achieved using a camrather than a setscrew 9 (not shown). Where a cam is substituted for asetscrew 9, locking of the arm 2 and joining of the arm 2 and the base 3is achieved by an analogous means.

Referring now to FIGS. 2A-C, 3A, 3B and 4, a support structure 10 isshown to which the connector end 12 of the arm 2 of the screw assembly 1can be attached (see FIGS. 3A, 3B and 4). As shown in FIG. 2A, thesupport structure 10 is comprised of a top surface 15, a bottom surface16, and one or more open-ended saddle receivers 11 including a setscrew9, or, in the alternative, a cam, for locking. The receiver 11 is shapedto accommodate the connector end 12 of the arm 2 of the screw assembly1. As shown in FIGS. 2A and 2B, the setscrew 9 is threaded into thesupport structure 10, perpendicular to the plane of the top surface 15of the support structure 10, to facilitate access to the setscrew 9 fromabove the support structure 10. In one implementation, the supportstructure 10 is comprised of two receivers 11 (see FIGS. 2A-C, 3A, 3Band 4), whereby two screw assemblies 1 can be linked together via thesupport structure 10 (see FIG. 3A). In another implementation, as shownin FIG. 3B, two screw assemblies 1 linked together via the supportstructure 10 can be implanted into the pedicles 26 of vertebrae 27 in aspine 28 to effect support of the spine 28.

As shown in FIGS. 2B and 4, the support structure 10 can be configuredto additionally include a central aperture 13 that passes from the topsurface 15 of the support structure 10 through to the bottom surface 16of the support structure 10. As shown in FIGS. 2B and 4, the centralaperture 13 can be threaded accommodate an anchor 14 and optionallyinclude a setscrew 9 or a cam for locking the anchor 14 in position. Inthis implementation the threading of the central aperture 13, andreceiver 11 setscrew(s) 9, are both aligned perpendicularly to the topsurface 15 of the support structure 10. The anchor 14 can be a screw,staple, hook or nail and be of a type typically used for bone anchoring.In one implementation, the anchor 14 is a screw of a type for insertioninto the pedicle 26 of a vertebrae 27.

In another implementation, as shown in FIG. 2C, the support structure 10can optionally include a hinged claw 21 for clamping the supportstructure 10 onto a surface (e.g., a bony surface). The claw 21 featuresa hinge 22 positioned between two receivers 11 in the support structure10. The claw 21 includes a threaded engagement member 23 extending abovethe top surface 15 of the support structure 10, whereby upon threading anut (not shown) over the engagement member 23, a pivoting about thehinge 22 is effected and the claw 21 closes.

The support structure 10 can be made of numerous materials that aredurable and that can be implanted within a body, including titanium,stainless steel, carbon fiber, biocompatible material, etc. Preferably,the screw assembly 1 is made of titanium. Additionally, the supportstructure 10 can be made of a reabsorbable material. Alternatively, thesupport structure 10 can be a composite or combination of any of theforegoing.

As shown in FIG. 5, another implementation of the invention includes asingle screw assembly 1, connected to a support structure 10 having areceiver 11, an anchor 14 and a locking means. In one implementation thereceiver 11 is configured as an open saddle-type head 6. In anotherimplementation, the support structure 10 includes a plurality ofreceivers 11. The locking means can include a setscrew 9 oralternatively a cam. In one implementation, the connector end 12 of thescrew assembly arm 2 is locked into the open saddle-type receiver head 6of the support structure 10 after the anchor is installed in a patient.

As shown in FIG. 6, a method of using the invention to support the spine28 includes the steps of: 1) making a series of small incisions alongthe spine 28 to provide cannula 29 access to the pedicle 26 portions ofa series of vertebrae 27; 2) using the cannula 29 access route, delivertwo un-deployed screw assemblies 1 to a series of pedicles 26 and screwthem into respective pedicles 26 (wherein un-deployed refers to aconfiguration of the screw assemblies 6 such that each arm 2 is set in aposition that is parallel to the long axis of the base 3); 3) using thecannula 29 access route and a support structure tool 30, deliver, screwinto place and lock a support structure 10 having a central aperture 13,set screw 9, two receivers 11 with setscrews 9 and pedicle screw-typeanchor 4; 4) deploy the arms 2 of each screw assembly 1 substantiallyperpendicular to the long axis of the base 3; 5), and engage and lockinto place each connector end 12 of each arm 2 within the supportstructure 10 receivers 11 using the set screws 9.

The above method includes the use of a special screw assembly tool 19for manipulation of the screw assemblies 1 (see FIG. 7). The screwassembly tool 19 includes an inner cavity 24 configured to accommodatethe un-deployed screw assembly 1 within it. In use, the screw assemblytool 19 facilitates the insertion of the un-deployed screw assembly 1base 3 into a structure (e.g., bone) from within the confines of acannula 29.

An additional method of use of the invention for supporting the spine,can include the steps of: 1) delivering to bone, two screw assemblies 1having arms 2, bases 3 and interconnection means 4; 2) delivering to thevicinity of bone, a support structure 10 having two receivers 11 havinglocking means for the arms 2 of the screw assemblies 1; 3) deploying thearms 2 of the screw assemblies 1; and 4) engaging the locking means ofthe receivers 11 to secure the arms 2 of the screw assembly 1 to thesupport structure 10.

Another method of use of the invention for supporting the spine, caninclude the steps of: 1) delivering to bone, two screw assemblies 1having arms 2, bases 3 and interconnection means 4; 2) delivering tobone, a support structure 10 having a central aperture 13 with a lockingmeans and an anchor 14, and two receivers 11 having locking means forthe arms 2 of the screw assemblies 1; 3) deploying the arms 2 of thescrew assemblies 1; and 4) engaging the locking means of the receivers11 to secure the arms 2 of the screw assemblies 1 to the supportstructure 10.

Yet another method of use of the invention for supporting the spine, caninclude the steps of: 1) delivering to bone, a screw assembly having anarm, base and interconnection means; 2) delivering to bone, a supportstructure having a central aperture with a locking means and an anchor,and a receiver having locking means for the arm of a screw assembly; 3)deploying the arm of the screw assembly; and 4) engaging the lockingmeans of the receiver to secure the arm of the screw assembly to thesupport structure.

The method of supporting the spine can also be used in conjunction witha kyphoplasty procedure. Kyphoplasty is a percutaneous techniqueinvolving the use of an expandable structure, such as a ballooncatheter, to create a cavity or void within the vertebral body, followedby filling the cavity with a bone substitute to form an “internal cast”.Methods and instruments suitable for such treatment are more fullydescribed in U.S. Pat. Nos. 4,969,888 and 5,108,404, which areincorporated herein by reference. Kyphoplasty can be used to reducevertebral compression fractures and to move bone with precision, thusrestoring as close to normal the natural alignment of the vertebralcolumn. Reduction of traumatic vertebral compression fractures havehistorically been treated with open reduction, internal fixationstabilization hardware and fusion techniques using a posterior approach.The usual role of stabilization hardware is to stop motion across thedisk so that bone graft can fuse one vertebral body to the next.Usually, the stabilization hardware is left in permanently. In traumarepair, stabilization hardware is used to offload the fracturedvertebral body so that the natural healing process can occur. In trauma,the stabilization hardware is designed to facilitate easy removal.Stabilization hardware can take many forms, including those describedherein. The combination of kyphoplasty and insertion of stabilizationhardware utilizing the naturally occurring interior muscle plane asdescribed in Wiltse and Spencer, Spine (1988) 13(6):696-706, satisfiesthe goals of improving the quality of patient care through minimallyinvasive surgical therapy.

A number of preferred embodiments of the invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the invention. Forexample, while the some implementations have been described using screwsto anchor into bony structures, the scope of the invention is not solimited. Any means of anchoring can be used, such as a cam, screw,staple, nail, pin, or hook. Accordingly, other embodiments are withinthe scope of the following claims.

1-36. (canceled)
 37. A method of supporting the spine, the methodcomprising the steps of: 1) delivering to bone, two screw assemblieshaving arms, bases and interconnection means; 2) delivering to thevicinity of bone, a support structure having two receivers havinglocking means for the arms of the screw assemblies; 3) deploying thearms of the screw assemblies; and 4) engaging the locking means of thereceivers to secure the arms of the screw assemblies to the supportstructure.
 38. A method of supporting the spine, the method comprisingthe steps of: 1) delivering to bone, two screw assemblies having arms,bases and interconnection means; 2) delivering to bone, a supportstructure having a central aperture with a locking means and an anchor,and two receivers having locking means for the arms of the screwassemblies; 3) deploying the arms of the screw assemblies; and 4)engaging the locking means of the receivers to secure the arms of thescrew assemblies to the support structure.
 39. A method of supportingthe spine, the method comprising the steps of: 1) delivering to bone, ascrew assembly having an arm, base and interconnection means; 2)delivering to bone, a support structure having a central aperture with alocking means and an anchor, and a receiver having locking means for thearm of a screw assembly; 3) deploying the arm of the screw assembly; and4) engaging the locking means of the receiver to secure the arm of thescrew assembly to the support structure. 40-44. (canceled)